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Title: Biota of selected aquatic habitats of the McClellan-Kerr Arkansas River Navigaton System
Authors: Environmental and Water Quality Operational Studies (U.S.)
Sanders, Larry G.
Baker, John A.
Bond, Carolyn L.
Pennington, C. H.
Keywords: Aquatic ecology
Arkansas River Navigation System
Benthic macroinvertebrates
Freshwater ecology
Publisher: Environmental Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Technical Report
Abstract: This report describes fish and benthic macroinvertebrate composition in five aquatic habitat types within Pool 5, river miles 89-102, of the McClellan-Kerr Arkansas River Navigation System. Two dike fields, including the dike structures themselves, two secondary channels, two natural banks, two revetted banks, and one abandoned channel were sampled during high- (June, >125,000 cfs) and low- (September, <10,000 cfs) flow periods during 1982. Within each sampling period, relatively small differences were observed among habitats in terms of dissolved oxygen, temperature, pH, and conductivity. During the June high-flow period, both current velocity and substrate composition varied considerably, with habitats located nearer the upstream end of the pool tending to have swifter currents and coarser substrates. During the September low-flow sampling, pooled conditions existed and current velocity and substrate were homogeneous. Fish populations differed most among habitats during the June high-flow period, when the habitats were physically most distinct. Fish spec1es composition was primarily a function of current velocity. Habitats characterized by higher velocities (the upstream-most revetted bank, natural bank, dike field, and secondary channel) supported primarily catfishes and freshwater drum. Habitats with slower, or slack, currents (downstream-most revetted bank, natural bank, dike field, and secondary channel, plus the abandoned channel) also included typical slack-water species (sunfishes, basses, crappies, gars, bowfin). During the September low-flow period, fish populations showed little difference among habitats, reflecting the increase in habitat physical similarity. The macroinvertebrate fauna colonizing the dike and revetment structures reflected the differences in physical conditions which existed in the study area during June. Those structures located near the upstream end of the study area were colonized principally by hydropsychid caddisfly larvae (Trichoptera), which are filter feeders and are therefore dependent upon current. Those structures located near the downstream end of the study area where currents were reduced exhibited a shift in dominance with polycentropodid caddisfly larvae and the Chironomidae (Diptera) constituting a majority of the benthic community in these habitats. This phenomenon, whereby different community composition could be directly correlated to varying current velocity, became more evident when comparing the fauna colonizing these structures in September to the community that had colonized the same habitats in June. With the absence of current in September, a typically lentic community existed at all habitats, with polycentropodid caddisfly larvae, the Chironomidae, and amphipods (Amphipoda) being the dominant groups collected at all habitats regardless of their location within the study area. The benthic communities that colonized the bottom substrates differed most among habitats during the June sampling effort due to the extreme differences in current velocities and substrate types present at the various habitats. Those areas subjected to high current velocities and erosional substrates (dike fields and natural banks) had low density estimates and little diversity as compared to those habitats (secondary and abandoned channels) in which little or no current existed and a relatively homogeneous substrate was present. Tubificid Oligochaetes (Oligochaeta) and the Chironomidae (Diptera) were the dominant macroinvertebrate groups collected at all habitats in June. Increases in density and diversity were noted for all habitats sampled in September as compared to June, with the natural bank habitat exhibiting the highest density estimates of all habitats sampled. This was due in part to the extremely high numbers of the amphipod Corophium lacustre (Amphipoda) collected at this habitat. The increase in density estimates and similarity among habitats in September is explained in part by the fact that physical conditions encountered during this time were somewhat similar in all habitats, unlike June when physical differences were observed over the entire length of the study area.
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